Top quality Evolution Aqua bio media. Plastic media, for use in biological Pond filters - specifically in moving bed bio reactors, was pioneered by Evolution Aqua. Evolution Aqua K + Advanced Media is moulded with minerals for faster beneficial bacteria development. K + Advanced media also has a much larger surface area than any other media. Unlike foam, matting, or other forms of static filtration media, the K+ Advanced Media is designed to move freely within your filter in a downflow filtration system. The constant chaotic movement of the air from your pump causes the media to self-clean and thus requires no maintenance this allows the filter to reach optimum effectiveness without the disturbance of periodic cleaning, avoiding unnecessary loss of bacteria within the filter. Specifications Product: K Plus Advanced Filter Media Gravity: Sinking Diameter: 10.5mm Total Surface Area: 1,350 m² per m³ Protected Surface Area: 1,025 m² per m³ Length: 8mm This media can filter particles down to one micron.